High mobility Ti, Zr and Ga-codoping In2O3 transparent conductive oxide films prepared at low temperatures

High mobility transparent conductive Zr, Ti and Ga-doped indium oxide (ITGZO) films were deposited by radio frequency (RF) magnetron sputtering method at the low deposition temperature. The effects of deposition temperatures on structural, electrical, and optical properties of ITGZO films were investigated in this work. High mobility of 94 cm2/V S was achieved at the deposition temperature of 70 °C along with the annealing process. Furthermore, the optical transmittance of ITGZO films has increased by 18% at the infrared wavelength region from 1500 to 2580 nm; compared to the typical Sn-doped indium oxide (ITO) films, this excellent transmittance is mainly attributed to the less free carrier absorption (FCA) thanks to the low carrier concentration of less than 2.0 × 1020 cm−3. In addition, the surface morphology of ITGZO films demonstrated that Ga element would precipitate on the film surface when oxygen was insufficient during the film growth, which indicates that Ga element exists as an oxidation state rather than interstitial atom in ITGZO films; correspondingly, the impurity ion scattering of carriers would be effectively suppressed, which accounts for the high mobility of ITGZO films. Moreover, ITGZO film shows a very low extinction coefficient (k) of 10–4 at 633 nm after annealing, which implies almost zero absorption loss from ITGZO films. Based on the higher mobility and better optical properties, it is expected that ITGZO film is a promising alternative material substituting for the typical ITO film in the advanced optoelectronic devices.